Water electrolysis method and device for determination of hydrogen and oxygen stable isotopic composition

Abstract

Water electrolysis device determining stable isotopic composition of water and a water electrolysis method for stable isotopic composition of water capable of analyzing many samples easily, safely and at low cost in very short time, and rapidly analyzing 17 O are provided. The water electrolysis device performing mass spectrometry of hydrogen or oxygen stable isotopic composition includes a proton exchange membrane of fluorocarbon polymer plated non-electrolytically with platinum, iridium, rhodium or iridium-rhodium alloy, and a cathode and an anode of porous titanium plated with platinum and sandwiching the proton exchange membrane, wherein water electrolyzes by introduction into the anode side chamber and supplying DC current between the anode and the cathode, and oxygen gas generated at the anode and hydrogen gas generated at the cathode respectively flows into an isotope ratio mass spectrometer. Water electrolysis method for stable isotopic composition of water using the water electrolysis device is also provided.

1. A water electrolysis device for determination of stable isotopic composition of water and performing mass spectrometry of one of hydrogen stable isotopic composition and oxygen stable isotopic composition, the water electrolysis device comprising a proton exchange membrane which is made of fluorocarbon polymer plated non-electrolytically with one of platinum, iridium, rhodium and iridium-rhodium alloy, and a cathode and an anode made of porous titanium plated with platinum and sandwiching the proton exchange membrane between them, wherein water is electrolyzed by introducing water into the anode side and supplying a DC current between the anode and the cathode, and oxygen gas generated at the anode and hydrogen gas generated at the cathode are respectively allowed to flow into an isotope ratio mass spectrometer. 
   
   
     2. The water electrolysis device according to  claim 1 , further comprising means for feeding nitrogen gas to each of a pathway which leads the oxygen gas generated at the anode to the isotope ratio mass spectrometer and a pathway which leads the hydrogen gas generated at the cathode to the isotope ratio mass spectrometer, whereby gas and water remaining in each pathway can be purged each time the oxygen gas or hydrogen gas is flown into the isotope ratio mass spectrometer. 
   
   
     3. The water electrolysis device for the determination of stable isotopic composition of water according to  claim 1 , further comprising a double-tube dehumidifying part in each of a pathway which leads the oxygen gas generated at the anode to the isotope ratio mass spectrometer and a pathway which leads the hydrogen gas generated at the cathode to the isotope ratio mass spectrometer, the double-tube dehumidifying part having an inner tube wall formed of a proton exchange membrane which is made of fluorocarbon polymer, wherein by letting air having dried with silica gel flow between an inner tube and an outer tube, only such water vapor which prevents mass spectrometric determination is removed from the oxygen gas or hydrogen gas flown into the inner tube, and thus the gases can be dehumidified before being introduced into the isotope ratio mass spectrometer. 
   
   
     4. A water electrolysis method of determining a stable isotopic composition of water for performing mass spectrometry of one of a hydrogen stable isotopic composition and an oxygen stable isotopic composition, the method comprising:
 electrolyzing sample water without adding any electrolyte; 
 separately extracting hydrogen gas and oxygen gas to introduce them into an isotope ratio mass spectrometer; and 
 conducting stable isotopic composition analysis of a hydrogen stable isotope and an oxygen stable isotope contained in the sample water. 
 
   
   
     5. The water electrolysis method for stable isotopic composition of water according to  claim 4 , wherein the electrolysis is conducted by using an electrolysis cell including a proton exchange membrane which is made of fluorocarbon polymer plated non-electrolytically with one of platinum, iridium, rhodium and iridium-rhodium alloy, and a cathode and an anode made of porous titanium plated with platinum and sandwiching the proton exchange membrane between them, in which water is electrolyzed by introducing water into an anode side chamber and supplying a DC current between the anode and the cathode. 
   
   
     6. A water electrolysis method of determining a stable isotopic composition of water, the method comprising:
 electrolyzing sample water without adding any electrolyte to extract oxygen gas; and 
 directly analyzing an oxygen isotope  17 O as a form of molecular oxygen electrolyzed from the sample water. 
 
   
   
     7. The water electrolysis method for stable isotopic composition of water according to  claim 6 , wherein the electrolysis is conducted by using an electrolysis cell including a proton exchange membrane which is made of fluorocarbon polymer plated non-electrolytically with one of platinum, iridium, rhodium and iridium-rhodium alloy, and a cathode and an anode made of porous titanium plated with platinum and sandwiching the proton exchange membrane between them, in which water is electrolyzed by introducing water into an anode side chamber and supplying a DC current between the anode and the cathode.